Add the 'G'/'g' and 'H'/'h' MALLOC_OPTIONS flags.
Add the malloc_tcache_flush() function.
Disable thread-specific caching until the application goes multi-threaded.
jemalloc is configured.
Modify arena_malloc() API to avoid unnecessary choose_arena() calls. Remove
unnecessary code from choose_arena().
Enable lazy-lock by default, now that choose_arena() is both faster and out of
the critical path.
Implement objdir support in the build system.